Project Title: Predatory Behavior of Great White Sharks

Overview

Sharks are apex predators throughout the ocean, yet relatively few studies have quantified or determined factors influencing their hunting behavior and predatory success rates. The waters off Southern Africa provide a unique opportunity to study predator-prey interactions involving Great White Sharks (hereafter white sharks). Since 1998, members of our team have been studying white sharks at Seal Island in False Bay. Our previous studies at this location have demonstrated that in the winter months, white sharks visit Seal Island to hunt Cape fur seals. About 48% of surface attacks on seals result in successful kills. Attack frequency is high, averaging 6.68 per day, with as many as 43 recorded in a single day. Sharks attack seals on the surface via a sudden vertical rush, which propels predator and prey out of the water in an awesome display of power and acrobatic prowess. While sightings of white sharks have declined in the recent years at Seal Island (see Hammerschlag et al. 2019), we have established a new research project at a new white shark hunting spot, located in the waters surrounding the Robberg Marine Protected Area (MPA) in Plettenberg Bay (Plett). Robberg MPA has become a new location for studying white shark and seal interactions. The cliffs of Robberg peninsula provides a unique vantage point for observing incredible shark hunting and seal counter attack behaviors. Our continued research at both Seal Island and Robberg in Plett Bay are two unparalleled opportunities to understanding the dynamcis between apex predators and they prey.

Some of the major questions we are currently investigating include:

1. Do white sharks make hunting decisions that optimize probability for prey capture?

2. What behaviors do sharks employ when hunting and attacking seals?

3. Do sharks exhibit evidence of learning or social behavior? If so, can these factors affect shark attack success rates?

4. Do white shark teeth function as mechanosensory structures, fostering tactile investigation?

5. Are shark hunting patterns at Seal Island random, clustered or dispersed?

6. What behaviors do seals use to avoid being attacked?

7. Do environmental factors influence a white shark’s ability to successfully capture seals and/or the seals’ ability to avoid being attacked?

Have you seen a Great White at Robberg in Plett?  Support our shark research and conservation by reporting your shark sighting in the LiveSpotr App.

Download LiveSpotr (it’s free!) on your mobile device to report your sighting. https://www.livespotr.com/Shark 

Recent Study Highlights & Examples

White sharks appear to hunt solitary juvenile Cape fur seals near their primary entry and exit point early in the morning, when light levels are low. Stalking is conducted from near the bottom, from sufficient depth to remain undetected during approach, and the attack launched vertically. This strategy maximizes a shark’s chance of catching a seal unaware, resulting in a fatal or incapacitating initial strike. Stealth and ambush are key elements in the white shark’s predatory strategy. Further, recognizable individual white sharks display distinct predatory strategies and some enjoy a predatory success rate of roughly 80%. Moreover, spatial patterns of shark predation at Seal Island are nonrandom. Sharks station themselves at specific points which represent an optimal balance among prey detection, capture rates, and competition. Smaller sharks exhibit more dispersed prey search patterns and have lower predatory success rates than larger conspecifics, suggesting possible learning with experience.

FIGURE (right): (A) Peak 1% geoprofile of 340 white shark attacks on Cape fur seals at Seal Island, South Africa, over primary seal travel path from and returning to the island (a triangle originating at LP and widening to the south; see Figure 1B); the geoprofile shows a strong, well-defined anchor point. (The ranges for the z-score — the likelihood value of the anchor point for a given pixel in a geoprofile — are depicted with different colours, outlined in the legend). Peak 1% geoprofiles of white shark attacks at Seal Island by total length, showing increasing focus of anchor point with increasing size (i.e., experience): (B) small sharks (<3 m); (C) medium sharks (3-3.5 m); and (D) large sharks (>3.5 m).Figure from Martin et al. 2009. Journal of Zoology, 279: 111-118

What is a breach attack?

Sharks attack seals on the surface via a sudden vertical rush, which propels predator and prey out of the water in an awesome display of power and acrobatic prowess.

What is their success rate?

Does every break attach result in a kill?

No! About 48% of surface attacks on seals result in successful kills. Attack frequency is high, averaging 6.68 per day, with as many as 43 recorded in a single day. Recognizable individual white sharks display distinct predatory strategies and some enjoy a predatory success rate of roughly 80%.

Scientific Publications

Hammerschlag N, Williams L, Fallows M, Fallows C. (2019) Disappearance of white sharks leads to the novel emergence of an allopatric apex predator, the sevengill shark. Scientific Reports; 9, 1908.

Skubel RA, Kirtman BP, Fallows C, Hammerschlag N (2018). Patterns of long-term climate variability and predation rates by a marine apex predator, the white shark Carcharodon carcharias. Marine Ecology Progress Series 587:129-139.

Hammerschlag N, Meÿer M, Seakamela S M, Kirkman S, Fallows C, Creel S. (2017) Physiological stress responses to natural variation in predation risk: evidence from white sharks and seals.Ecology, 98: 3199–3210.

Fallows C, Fallows M, Hammerschlag N. (2016). Effects of lunar phase on predator-prey interactions between white shark (Carcharodon carcharias) and Cape fur seals (Arctocephalus pusillus pusillus ). Environmental Biology of Fishes; 99(11): 805-812.

Fallows C, Gallagher AJ, Hammerschlag N (2013). White Sharks (Carcharodon carcharias) Scavenging on Whales and Its Potential Role in Further Shaping the Ecology of an Apex Predator.PLoS ONE 8(4): e60797. doi:10.1371/journal.pone.0060797.

Martin RA, Hammerschlag N. (2012). Marine predator-prey contests: Ambush and speed versus vigilance and agility, Marine Biology Research. 8:1, 90–94

Fallows C, Martin RA, Hammerschlag N. (2012). Comparisons between white shark-pinniped interactions at Seal Island (South Africa) with other sites in California (United States). In: Global Perspectives on the Biology and Life History of the White Shark, ed. Michael L. Domeier, Chapter 9, CRC Press, Boca Raton, FL.

Hammerschlag N, Martin RA, Fallows C, Collier R, Lawrence R. (2012). Investigatory Behavior towards surface objects and Non-consumptive Strikes on Seabirds by White Sharks (Carcharodon carcharias) at Seal Island, South Africa (1997–2010 In: Global Perspectives on the Biology and Life History of the White Shark, ed. Michael L. Domeier, Chapter 8, CRC Press, Boca Raton, FL.

Martin RA, Rossmo DK, Hammerschlag N. (2009). Hunting patterns and geographic profiling of white shark predation. Journal of Zoology, 279: 111–118.

Hammerschlag N, Martin RA, Fallows C. (2006). Effects of environmental conditions on predator-prey interactions between white sharks (Carcharodon carcharias) and Cape fur seals (Arctocephalus pusillus pusillus) at Seal Island, South Africa. Environmental Biology of Fishes 76: 341–350.

Martin RA, Hammerschlag N, Collier R, Fallows C. (2005). Predatory Behaviour of White Sharks (Carcharodon carcharias) at Seal Island, South Africa. Journal of the Marine Biological Association of the UK, 85: 1121–1135.

Hammerschlag N. (2004).Factors affecting predatory success of White Sharks (Carcharodon carcharias) at Seal Island in False Bay, South Africa. Nova Southeastern University Publication, Masters Thesis, 85 pp

Conservation Connection

Predator-prey interactions are of central importance in ecology, with important implications for population dynamics, management, and conservation. Sharks are top predators in many marine communities, yet few studies have quantified or determined those factors influencing their distribution and hunting behavior. However, studies of large shark foraging behavior are important for understanding the ecology of these species and are particularly important at this time in light of steep declines in their populations (e.g. Baum et al.,2003; Dulvy et al., 2008) and the recent realization that they may have important structuring roles in marine communities. Excerpted from Martin, Rossmo & Hammerschlag. (2009, Journal of Zoology, 279: 111-118)